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Numerical investigations on drag reduction of a civil light helicopter fuselage
Aerospace Science and Technology ( IF 5.6 ) Pub Date : 2020-07-23 , DOI: 10.1016/j.ast.2020.106104
Wenbo Shi , Jie Li , Haoxue Gao , Heng Zhang , Zhao Yang , Youxu Jiang

The paper presents the numerical investigations for a light civil helicopter fuselage with the purpose of reducing the helicopter drag. Two numerical methods: Reynolds-Averaged Navier-Stokes (RANS) and a hybrid RANS-LES method: improved delayed detached-eddy simulation (IDDES) method are performed for the simulation of a prototype helicopter fuselage. The RANS method is validated by a modular helicopter fuselage with experimental data, while the IDDES method has already been used in other studies and good results have been achieved. The numerical results of the civil helicopter in terms of the aerodynamic coefficients obtained by the two methods are consistent with each other. Compared to the RANS method, the IDDES approach is capable of predicting the large separation flow of the fuselage/components and the small-scale vortices in the flow field. It is found that the hybrid method captures the periodically detached separating vortices behind the skid struts, while the flow at the same position simulated by the RANS method is still attached. Moreover, separating vortices, which develop diagonally upwards, are captured at fuselage/tail-boom junction by the hybrid method, whereas RANS simulation doesn't predict. Subsequently, the design of the helicopter drag reduction is carried out at α=0 deg angle of attack and 0.2 Mach number through shape optimization based on the numerical simulations, and the numerical results are verified by the force tests. It shows that the optimization of the landing skids aims at reducing the strong Karman vortex shedding effect induced by the skids, which greatly decreases the total drag. Combined with the optimization of the fuselage/tail-boom transition, this approach suppresses the separation flow of the fuselage and reduces the pressure drag, and the adjustment of transition slope benefits of up to 1.18% drag reduction, while the extension of transition reduces the drag by 2.64%. The optimization of tail-boom layout demonstrates that lower tail-boom layout can contribute to a drag reduction by 4.37% (RANS) and 3.89% (test), respectively, when compared to the original tail-boom layout.



中文翻译:

民用轻型直升机机身减阻的数值研究

本文介绍了一种轻型民用直升机机身的数值研究,目的是减少直升机的阻力。两种数值方法:雷诺平均纳维-斯托克斯(RANS)方法和混合RANS-LES方法:改进的延迟分离涡模拟(IDDES)方法用于模拟原型直升机机身。RANS方法已通过具有实验数据的模块化直升机机身进行了验证,而IDDES方法已被用于其他研究中并取得了良好的结果。用两种方法得到的民用直升机在空气动力学系数方面的数值结果是一致的。与RANS方法相比,IDDES方法能够预测机身/组件的大分离流和流场中的小规模旋涡。发现混合方法捕获了滑撑后的周期性分离的分离涡流,而仍通过RANS方法模拟的相同位置处的流动仍然存在。此外,通过混合方法在机身/尾臂交界处捕获了向上倾斜延伸的分离涡流,而RANS模拟无法预测。随后,在以下位置进行直升机减阻的设计α=0通过数值模拟,通过形状优化优化了攻角和0.2马赫数,并通过力试验验证了数值结果。结果表明,对着陆滑道的优化旨在降低滑道引起的强烈的卡曼涡旋脱落效应,从而大大降低总阻力。结合优化的机身/尾部动臂过渡,该方法抑制了机身的分离流并降低了压力阻力,而过渡坡度的调整最多可减少阻力1.18%,而过渡的延伸则减少了阻力。拖动2.64%。尾吊杆布局的优化表明,与原始的尾吊杆布局相比,较低的尾吊杆布局可分别使阻力降低4.37%(RANS)和3.89%(测试)。

更新日期:2020-07-23
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